1. Field of the Invention
This invention relates generally to a system for measuring the time difference between successive periods in a waveform, and more particularly to a Gallium-Arsenide (GaAs) Differential Time Measurement Chip that implements time discrimination using only a single chip.
2. Background of the Invention
Electronic warfare systems sometimes require the demodulation of aperiodic, asynchronous frequency transients in pulsed radio frequency signals. Quantitatively determining the time differences in successive periods of a waveform is essential to many electronic warfare applications. For example, in radar systems of the type capable of tracking a moving target, information as to each movement of the target is contained in the reflected signal. Change in position of the target can be determined by sensing the time change of successive periods of the reflected signal. In response to the change, an antenna may be automatically repositioned.
Advanced systems generally require resolution of time period differences of less than 10 pico-seconds. The use of high speed counters, common to many systems, is impractical to resolve such small time differences because extremely large clock rates, nearing 10 GHz, would be required. Further, the requirement of 10 psec resolution precludes the use of discrete components to implement this function. As a result, it is desirable to implement the time discrimination function using only integrated components on a single chip.
The present invention represents an improved time discriminator that is incorporated on only a single GaAs chip. Monolithic design has numerous advantages over a discrete configuration. Improved resolution and reduced power consumption result from the better device matching and reduced parasitic capacitances. Further, the GaAs system possesses a fast switching time and high linearity. These advantages make monolithic design ideal for implementation of a time discrimination function.
U.S. Pat. No. 3,641,443 discloses a prior art time discriminator. However, the design disclosed therein does not lead itself to incorporation into an IC in a practical matter. In addition, the response of the known discriminator can be improved.